Re: [Devel] [PATCH hci-8.1 1/2] mm/memcontrol: allocate numa_migrate targets of the source folio order

[no-reply@sashiko.virtuozzo.com]

> memcg_numa_migrate_new_folio() treats every large folio as a PMD-sized
> THP and allocates an HPAGE_PMD_ORDER destination for it. The branch is
> the 4.18 pattern of new_page() in mm/mempolicy.c: a compound page on
> the LRU could only be a THP then, so PageTransHuge() implied
> HPAGE_PMD_ORDER.
> 
> Today the page cache holds large folios of any order (NFS sizes a folio
> to the write, XFS and shmem have them too) and anonymous memory has
> mTHP, while folio_test_large() is still just folio_test_head() and is
> true for any order from 1 up. migrate_pages() never checks that the
> destination order matches the source.
> 
> For an order-1 or order-4 file folio the destination is an order-9
> folio that inherits the source index and page cache reference count,
> so every later page cache operation that sizes the folio by its order
> [ ... ]
> Fixes: 9f8a754ad6c2 ("mm: memcontrol: add memory.numa_migrate file")
> https://virtuozzo.atlassian.net/browse/VSTOR-151607
> 
> Feature: mm: interface to migrate memory between NUMA nodes upon userspace request
> Signed-off-by: Konstantin Khorenko <khorenko@virtuozzo.com>

Sashiko has reviewed this patch and found no issues. It looks great!

-- 
Sashiko AI review · https://sashiko.vzint.dev/#/patchset/20261028-b4-prep-khorenko-vstor-151607-numa-migrate-order-v1-0-268336526677@virtuozzo.com?part=1


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